The definition, agreement and practical use of units of measurement have played a crucial role in human endeavour from early ages up to this day. Disparate systems of measurement used to be very common. Now there is a global standard, the International System (SI) of units, the modern form of the metric system. The SI has been or is in the process of being adopted throughout the world. In trade, weights and measures is often a subject of governmental regulation, to ensure fairness and transparency. The Bureau international des poids et mesures (BIPM) is tasked with ensuring worldwide uniformity of measurements and their traceability to the International System of Units (SI). Metrology is the science for developing national and internationally accepted units of weights and measures. Image File history File linksMetadata Download highresolution version (2048x1536, 790 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Imperial unit Units of measurement Metadata This file contains additional information, probably added from the digital camera or...
Image File history File linksMetadata Download highresolution version (2048x1536, 790 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Imperial unit Units of measurement Metadata This file contains additional information, probably added from the digital camera or...
The Middlesex Guildhall at Westminster Middlesex is one of the 39 historic counties of England and was the second smallest (after Rutland). ...
For other uses, see England (disambiguation). ...
A system of measurement is a set of units which can be used to specify anything which can be measured and were historically important, regulated and defined because of trade and internal commerce. ...
Look up si, Si, SI in Wiktionary, the free dictionary. ...
The International System of Units (symbol: SI) (for the French phrase Syst me International dUnit s) is the most widely used system of units. ...
Metrication or metrification refers to the introduction of the SI metric system as the international standard for physical measurementsâ€”a longterm series of independent and systematic conversions from the various separate local systems of weights and measures. ...
The Bureau International des Poids et Mesures (International Bureau of Weights and Measures, or BIPM) is a standards organization, one of the three organizations established to maintain the SI system under the terms of the Metre Convention. ...
Metrology (from Greek metron (measure), and logy) is the science of measurement. ...
In physics and metrology, units are standards for measurement of physical quantities that need clear definitions to be useful. Reproducibility of experimental results is central to the scientific method. A standard system of units facilitates this. Scientific systems of units are a refinement of the concept of weights and measures developed long ago for commercial purposes. A magnet levitating above a hightemperature superconductor demonstrates the Meissner effect. ...
Metrology (from Greek metron (measure), and logy) is the science of measurement. ...
Measurement is the estimation of the magnitude of some attribute of an object, such as its length or weight, relative to a unit of measurement. ...
A physical quantity is either a quantity within physics that can be measured (e. ...
This article is in need of attention from an expert on the subject. ...
Scientific method is a body of techniques for investigating phenomena, acquiring new knowledge, or correcting and integrating previous knowledge. ...
Science, medicine, and engineering often use larger and smaller units of measurement than those used in day to day life and talk about them more exactly. The judicious selection of the units of measure can aid researchers in problem solving (see, for example dimensional analysis). A magnet levitating above a hightemperature superconductor demonstrates the Meissner effect. ...
For the chemical substances known as medicines, see medication. ...
Engineering is the discipline of acquiring and applying knowledge of design, analysis, and/or construction of works for practical purposes. ...
Problem solving forms part of thinking. ...
Dimensional analysis is a conceptual tool often applied in physics, chemistry, and engineering to understand physical situations involving a mix of different kinds of physical quantities. ...
History

A unit of measurement is a standardised quantity of a physical property, used as a factor to express occurring quantities of that property. Units of measurement were among the earliest tools invented by humans. Primitive societies needed rudimentary measures for many tasks: constructing dwellings of an appropriate size and shape, fashioning clothing, or bartering food or raw materials. Some humanreferenced units of measurement Units of measurement were among the earliest tools invented by humans. ...
Quantity is a kind of property which exists as magnitude or multitude. ...
A baby wearing many items of winter clothing: headband, cap, furlined coat, shawl and sweater. ...
Barter is a simple form of trade where goods or services are exchanged for a certain amount of other goods or services, i. ...
The earliest known uniform systems of weights and measures seem to have all been created sometime in the 4th and 3rd millennia BC among the ancient peoples of Mesopotamia, Egypt and the Indus Valley, and perhaps also Elam in Persia as well. The 4th millennium BC saw major changes in human culture. ...
The 3rd millennium BC spans the Early to Middle Bronze Age. ...
Mesopotamia was a cradle of civilization geographically located between the Tigris and Euphrates rivers, largely corresponding to modernday Iraq. ...
Excavated ruins of Mohenjodaro. ...
Elam (Persian: ØªÙ…Ø¯Ù† Ø§ÛŒÙ„Ø§Ù…) is one of the oldest recorded civilizations. ...
Anthem SorÅ«de MellÄ«e ÄªrÄn Â² Capital (and largest city) Tehran Official languages Persian Demonym Iranian Government Islamic Republic  Supreme Leader  President Unification  Unified by Cyrus the Great 559 BCE  Parthian (Arsacid) dynastic empire (first reunification) 248 BCE224 CE  Sassanid dynastic empire 224â€“651 CE  Safavid dynasty...
Many systems were based on the use of parts of the body and the natural surroundings as measuring instruments. Our present knowledge of early weights and measures comes from many sources.
Systems of measurement Traditional systems
This derivation of the Vitruvian Man by Leonardo da Vinci, depicts nine historical units of measurement: the Yard, the Span, the Cubit, the Flemish Ell, the English Ell, the French Ell, the Fathom, the Hand , and the Foot. The Vitruvian man was drawn to scale, so the units depicted are displayed with their proper historical ratios. Prior to the global adoption of the metric system many different systems of measurement had been in use. Many of these were related to some extent or other. Often they were based on the dimensions of the human body. As a result, units of measure could vary not only from location to location, but from person to person. Image File history File links No higher resolution available. ...
Image File history File links No higher resolution available. ...
Leonardo da Vincis Vitruvian Man (1492). ...
â€œDa Vinciâ€ redirects here. ...
A yard (abbreviation: yd) is the name of a unit of length in a number of different systems, including English units, Imperial units, and United States customary units. ...
This does not cite any references or sources. ...
This derivation of the Vitruvian Man by Leonardo da Vinci, depicts nine historical units of measurement: the Yard, the Span, the Cubit, the Flemish Ell, the English Ell, the French Ell, the Fathom, the Hand , and the Foot. ...
An ell, when used as a unit of length, is usually 45 inches, i. ...
A fathom is the name of a unit of length in the Imperial system (and the derived U.S. customary units). ...
A hand (or handbreadth) is a unit of length measurement, usually based on the breadth of a male human hand and thus around 1 dm, i. ...
This article is about a foot as a unit of length. ...
Metric systems A number of metric systems of units have evolved since the adoption of the original metric system in France in 1791. The current international standard metric system is the International system of units. An important feature of modern systems is standardization. Each unit has a universally recognized size. The International System of Units (symbol: SI) (for the French phrase Syst me International dUnit s) is the most widely used system of units. ...
Look up si, Si, SI in Wiktionary, the free dictionary. ...
â€œStandardâ€ redirects here. ...
Both the Imperial units and US customary units derive from earlier English units. Imperial units were mostly used in the British Commonwealth and the former British Empire. US customary units are still the main system of measurement in the United States despite Congress having legally authorized metric measure on 28 July 1866^{[1]}, as amended by Public Law 110–69 Aug 9, 2007. Some steps towards US metrication have been made, particularly the redefinition of basic US units in order to exactly derive from SI units, so that in the US, the inch is now defined as 0.0254 m, and the avoirdupois pound is now defined as 453.59237 g. This article is about post1824 imperial units, see also English unit, U.S. customary units or Avoirdupois. ...
The U.S. customary units (more commonly known in the US as English units or standard units) are the nonmetric units of measurement that are presently used in the United States, in some cases alongside the metric system of units. ...
English unit is the American name for a unit in one of a number of systems of units of measurement, some obsolete, and some still in use. ...
The Commonwealth of Nations as of 2007 Headquarters Marlborough House, London, UK Official languages English Membership 53 sovereign states Leaders  Queen Elizabeth II  SecretaryGeneral Kamalesh Sharma Appointed 24 November 2007 Establishment  Balfour Declaration 18 November 1926  Statute of Westminster 11 December 1931  London Declaration 28 April 1949 Area  Total...
The British Empire in 1897, marked in pink, the traditional colour for Imperial British dominions on maps. ...
is the 209th day of the year (210th in leap years) in the Gregorian calendar. ...
1866 (MDCCCLXVI) is a common year starting on Monday of the Gregorian calendar or a common year starting on Wednesday of the 12dayslower Julian calendar. ...
August 9 is the 221st day of the year in the Gregorian Calendar (222nd in leap years), with 144 days remaining. ...
Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ...
Metrication or metrification refers to the introduction of the SI metric system as the international standard for physical measurementsâ€”a longterm series of independent and systematic conversions from the various separate local systems of weights and measures. ...
Natural systems While the above systems of units are based on arbitrary unit values, formalised as standards, some unit values occur naturally in science. Systems of units based on these are called natural units. Similar to natural units, atomic units (au) are a convenient system of units of measurement used in atomic physics. In physics, natural units are physical units of measurement defined in terms of universal physical constants in such a manner that some chosen physical constants take on the numerical value of one when expressed in terms of a particular set of natural units. ...
Atomic units (au) form a system of units convenient for electromagnetism, atomic physics, and quantum electrodynamics, especially when the focus is on the properties of electrons. ...
In physics and metrology, units are standards for measurement of physical quantities that need clear definitions to be useful. ...
Atomic physics (or atom physics) is the field of physics that studies atoms as isolated systems comprised of electrons and an atomic nucleus. ...
Also a great number of strange and nonstandard units may be encountered. These may include: the solar mass, the ton of TNT, the Hiroshima atom bomb and the weight of an elephant. Strange and whimsical units are sometimes used by scientists, especially physicists and mathematicians, and other technicallyminded people such as engineers and programmers, as bits of dry humor combined with putative practical convenience. ...
Rphrases Sphrases Related Compounds Related compounds picric acid hexanitrobenzene Except where noted otherwise, data are given for materials in their standard state (at 25 Â°C, 100 kPa) Infobox disclaimer and references Trinitrotoluene (TNT) is a chemical compound with the formula C6H2(NO2)3CH3. ...
For other uses, see Hiroshima (disambiguation). ...
The mushroom cloud of the atomic bombing of Nagasaki, Japan, in 1945 lifted nuclear fallout some 18 km (60,000 feet) above the epicenter. ...
Genera and Species Loxodonta Loxodonta cyclotis Loxodonta africana Elephas Elephas maximus Elephas antiquus â€ Elephas beyeri â€ Elephas celebensis â€ Elephas cypriotes â€ Elephas ekorensis â€ Elephas falconeri â€ Elephas iolensis â€ Elephas planifrons â€ Elephas platycephalus â€ Elephas recki â€ Stegodon â€ Mammuthus â€ Elephantidae (the elephants) is a family of pachyderm, and the only remaining family in the order Proboscidea...
Base and derived units Different systems of units are based on different choices of a set of fundamental units. The most widely used system of units is the International System of Units, or SI. There are seven SI base units. All other SI units can be derived from these base units. A set of fundamental units is a set of units for physical quantities from which every other unit can be generated. ...
Look up si, Si, SI in Wiktionary, the free dictionary. ...
The SI system of units defines seven SI base units: physical units defined by an operational definition. ...
SI derived units are part of the SI system of measurement units and are derived from the seven SI base units. ...
For most quantities a unit is absolutely necessary to communicate values of that physical quantity. For example, conveying to someone a particular length without using some sort of unit is impossible, because a length cannot be described without a reference used to make sense of the value given. But not all quantities require a unit of their own. Using physical laws, units of quantities can be expressed as combinations of units of other quantities. Thus only a small set of units is required. These units are taken as the base units. Other units are derived units. Derived units are a matter of convenience, as they can be expressed in terms of basic units. Which units are considered base units is a matter of choice. The base units of SI are actually not the smallest set. Smaller sets have been defined. There are sets in which the electric and magnetic field have the same unit. This is based on physical laws that show that electric and magnetic field are actually different manifestations of the same phenomenon. The SI system of units defines seven SI base units: physical units defined by an operational definition. ...
In physics, the space surrounding an electric charge or in the presence of a timevarying magnetic field has a property called an electric field. ...
For the indiepop band, see The Magnetic Fields. ...
Calculations with units Units as dimensions Any value of a physical quantity is expressed as a comparison to a unit of that quantity. For example, the value of a physical quantity Z is written as the product of a unit [Z] and a numerical factor: A physical quantity is either a quantity within physics that can be measured (e. ...
The multiplication sign is usually left out, just as it is left out between variables in scientific notation of formulas. In formulas the unit [Z] can be treated as if it were a kind of physical dimension: see dimensional analysis for more on this treatment. 2dimensional renderings (ie. ...
Dimensional analysis is a conceptual tool often applied in physics, chemistry, and engineering to understand physical situations involving a mix of different kinds of physical quantities. ...
A distinction should be made between units and standards. A unit is fixed by its definition, and is independent of physical conditions such as temperature. By contrast, a standard is a physical realization of a unit, and realizes that unit only under certain physical conditions. For example, the metre is a unit, while a metal bar is a standard. One metre is the same length regardless of temperature, but a metal bar will be one metre long only at a certain temperature.
Guidelines  Treat units like variables. Only add like terms. When a unit is divided by itself, the division yields a unitless one. When two different units are multiplied, the result is a new unit, referred to by the combination of the units. For instance, in SI, the unit of speed is metres per second (m/s). See dimensional analysis. A unit can be multiplied by itself, creating a unit with an exponent (e.g. m²/s²).
 Some units have special names, however these should be treated like their equivalents. For example, one newton (N) is equivalent to one kg·m/s². This creates the possibility for units with multiple designations, for example: the unit for surface tension can be referred to as either N/m (newtons per metre) or kg/s² (kilograms per second squared).
Dimensional analysis is a conceptual tool often applied in physics, chemistry, and engineering to understand physical situations involving a mix of different kinds of physical quantities. ...
This box: Surface tension is an effect within the surface layer of a liquid that causes that layer to behave as an elastic sheet. ...
Expressing a physical value in terms of another unit Conversion of units involves comparison of different standard physical values, either of a single physical quantity or of a physical quantity and a combination of other physical quantities. Conversion of units refers to conversion factors between different units of measurement for the same quantity. ...
Starting with: just replace the original unit [Z]_{i} with its meaning in terms of the desired unit [Z]_{j}, e.g. if , then: Now n_{i} and c_{ij} are both numerical values, so just calculate their product. Or, which is just mathematically the same thing, multiply Z by unity, the product is still Z: For example, you have an expression for a physical value Z involving the unit feet per second ([Z]_{i}) and you want it in terms of the unit miles per hour ([Z]_{j}):  Find facts relating the original unit to the desired unit:
 1 mile = 5280 feet and 1 hour = 3600 seconds
 Next use the above equations to construct a fraction that has a value of unity and that contains units such that, when it is multiplied with the original physical value, will cancel the original units:
 Last,multiply the original expression of the physical value by the fraction, called a conversion factor, to obtain the same physical value expressed in terms of a different unit. Note: since valid conversion factors are dimensionless and have a numerical value of one, multiplying any physical quantity by such a conversion factor (which is 1) does not change that physical quantity.
Or as an example using the metric system, you have a value of fuel economy in the unit litres per 100 kilometres and you want it in terms of the unit microlitres per metre: This article lists conversion factors between a number of units of measurement. ...
In the physical sciences, a dimensionless number (or more precisely, a number with the dimensions of 1) is a quantity which describes a certain physical system and which is a pure number without any physical units; it does not change if one alters ones system of units of measurement...
One redirects here. ...
Realworld implications One example of the importance of agreed units is the failure of the NASA Mars Climate Orbiter, which was accidentally destroyed on a mission to the planet Mars in September 1999 instead of entering orbit, due to miscommunications about the value of forces: different computer programs used different units of measurement (newton versus pound force). Enormous amounts of effort, time, and money were wasted.^{[2]}^{[3]} For other uses, see NASA (disambiguation). ...
Artists conception of the Mars Climate Orbiter Mars Climate Orbiter during tests The Mars Climate Orbiter (formerly the Mars Surveyor 98 Orbiter) was one of two spacecraft in the Mars Surveyor 98 program, the other being the Mars Polar Lander (formerly the Mars Surveyor 98 Lander). ...
This article is about the astronomical term. ...
Mars is the fourth planet from the Sun in the solar system, named after the Roman god of war (the counterpart of the Greek Ares), on account of its blood red color as viewed in the night sky. ...
Two bodies with a slight difference in mass orbiting around a common barycenter. ...
For other uses, see Newton (disambiguation). ...
A pound or poundforce (abbreviations: lb, lbf, or lbf) is a unit of force. ...
On April 15, 1999 Korean Air cargo flight 6316 from Shanghai to Seoul was lost due to the crew confusing tower instructions (in metres) and altimeter readings (in feet). Three crew and five people on the ground were killed. Thirty seven were injured.^{[2]}^{[4]} is the 105th day of the year (106th in leap years) in the Gregorian calendar. ...
Events of 2008: (EMILY) Me Lesley and MIley are going to China! This article is about the year. ...
Korean Air (formerly Korean Air Lines) (KRXS: 003490) (Korean Air Daehan Hanggong) is the flag carrier airline of Korea, its global headquarters are located in Seoul, Korea. ...
For other uses, see Shanghai (disambiguation). ...
Short name Statistics Location map Map of location of Seoul. ...
References  Appendix B of NIST Handbook 44, (2002) National Institute of Science and Technology
External links  Perspectives on the magnitude of various units of measure. Database for examination.
 Unit Conversion : Oil Industry Conversions
 Official SI website
 Canada  Weights and Measures Act 19707172
 Ireland  Metrology Act 1996
 UK  Units of Measurement Regulations 1995
 UK Metric Association
 US Metric Association
 The Unified Code for Units of Measure (UCUM)
 A Dictionary of Units of Measurement  Center for Mathematics and Science Education, University of North Carolina
A system of measurement is a set of units which can be used to specify anything which can be measured and were historically important, regulated and defined because of trade and internal commerce. ...
The International System of Units (symbol: SI) (for the French phrase Syst me International dUnit s) is the most widely used system of units. ...
â€œSIâ€ redirects here. ...
This article or section is in need of attention from an expert on the subject. ...
The metretonnesecond or mts system of units is a system of physical units introduced in the Soviet Union in 1933, but abolished in 1955. ...
The unit kilogramforce (kgf, often just kg) or kilopond (kp) is defined as the force exerted by one kilogram of mass in standard Earth gravity. ...
In physics, natural units are physical units of measurement defined in terms of universal physical constants in such a manner that some chosen physical constants take on the numerical value of one when expressed in terms of a particular set of natural units. ...
In physics, especially in the general theory of relativity, geometrized units or geometric units constitute a physical unit system in which all physical quantities are identified with geometric quantities such as areas, lengths, dimensionless numbers, path curvatures, or sectional curvatures. ...
In physics, Planck units are physical units of measurement defined exclusively in terms of the five universal physical constants shown in the table below in such a manner that all of these physical constants take on the numerical value of one when expressed in terms of these units. ...
In physics, natural units are physical units of measurement defined in terms of universal physical constants in such a manner that some chosen physical constants take on the numerical value of one when expressed in terms of a particular set of natural units. ...
In physics, natural units are physical units of measurement defined in terms of universal physical constants in such a manner that some chosen physical constants take on the numerical value of one when expressed in terms of a particular set of natural units. ...
Atomic units (au) form a system of units convenient for electromagnetism, atomic physics, and quantum electrodynamics, especially when the focus is on the properties of electrons. ...
In physics, natural units are physical units of measurement defined in terms of universal physical constants in such a manner that some chosen physical constants take on the numerical value of one when expressed in terms of a particular set of natural units. ...
In physics, natural units are physical units of measurement defined in terms of universal physical constants in such a manner that some chosen physical constants take on the numerical value of one when expressed in terms of a particular set of natural units. ...
The avoirdupois (IPA: ; French IPA: ) system is a system of weights (or, properly, mass) based on a pound of sixteen ounces. ...
Troy ounce is a traditional unit of gold weight. ...
The apothecaries system of mass is an obsolete system formerly used by apothecaries (now called pharmacists or chemists) in Englishspeaking countries. ...
English unit is the American name for a unit in one of a number of systems of units of measurement, some obsolete, and some still in use. ...
This article is about post1824 imperial units, see also English unit, U.S. customary units or Avoirdupois. ...
U.S. customary units, also known in the United States as English units[1] (but see English unit) or standard units, are units of measurement that are currently used in the USA, in some cases alongside units from SI (the International System of Units â€” the modern metric system). ...
This article needs to be cleaned up to conform to a higher standard of quality. ...
The Dutch system was not standardised until Napoleon introduced the metric system. ...
In Finland, approximate units of measure were derived from natural actions or objects such body parts, later standardised for the purpose of commerce. ...
In France, before the decimalised metric system of 1799, a welldefined old system existed, however with some local variants. ...
Germany had an indigenous system of German units of measurement prior to its adoption of the international metric system. ...
In modern usage, metric is used almost exclusively in commercial transactions. ...
As in the case of the Danes the Norwegians earliest standards of measure can be derived from their ship burials. ...
Several native system of weights and measures were used in Scotland. ...
There are a number of Spanish and Portuguese units of measurement of length or area that are now obsolete. ...
In Sweden, a common system for weights and measures was introduced by law in 1665. ...
Ancient Polish weights and measures included: Garniec [1] Grzywna [2] and [3] KamieÅ„ [4] Korzec [5] Krok [6] Kwarta [7] Kwartnik [8] Åan [9] Åaszt [10] Åawka [11] ÅokieÄ‡ [12] Åut [13] Morga [14] Pacierz [15] PiÄ™dÅº [16] Skojec [17] Staje [18] Stopa [19] Wiardunek [20] ZdrowaÅ›ka [21...
The measures of the old Romanian system varied greatly not only between the three Romanian states (Wallachia, Moldavia, Transylvania), but sometimes also inside the same country. ...
Obsolete Russian weights and measures were used in Imperial Russia and after the Russian Revolution until they were replaced in the Soviet Union by a metric system in 1924. ...
Obsolete Tatar weights and measures were used by Tatars until 1924, when they were replaced in the Soviet Union by the SI units. ...
Old Indian measures are still in use today, primarily for religious purposes in Hinduism and Jainism. ...
This article or section does not cite any references or sources. ...
The Chinese units (Chinese: å¸‚åˆ¶; Hanyu Pinyin: ; literally market system) are the customary and traditional units of measure used in China. ...
ShakkanhÅ ) is the traditional Japanese system of measurement. ...
Taiwanese units of measurement (Traditional Chinese: ; pinyin: ; Minnan: TÃ¢ichoÃ¨) are the customary and traditional units of measure used in Taiwan. ...
Ancient Greek weights and measures  Wikipedia, the free encyclopedia /**/ @import /skins1. ...
The Roman system of measurement was built on the Greek system with Egyptian influences. ...
This article needs to be cleaned up to conform to a higher standard of quality. ...
Weight Reduced to English troyweight, the Hebrew weights were: Gerah (Lev. ...
The Arabic system of measurement is based on the Persian system. ...
Originally Ancient Mesopotamian weights and measures came from a collection of city states loosely organized by family, tribe and occupation. ...
This article needs to be cleaned up to conform to a higher standard of quality. ...
This article does not cite its references or sources. ...
Unusual units of measurement are sometimes used by scientists, especially physicists and mathematicians, and other technicallyminded people such as engineers and programmers, as bits of dry humor combined with putative practical convenience. ...
Mesures usuelles (French for customary measurements) were a system of measurement introduced to act as compromise between metric system and traditional measurements. ...
